The Atlantic goliath grouper, found in warm waters of the Americas and western Africa, is a separate species from the goliath grouper that roams tropical reefs of the eastern Pacific Ocean, a new genetic study shows.
The newly identified Pacific goliath grouper can grow more than 6 feet (1.8 meters) long and weighs nearly 1,000 pounds (454 kilograms).
Since the oceangoing giants are identical in body shape and markings, scientists hadn't thought to analyze their genes.
"For more than a century, ichthyologists have thought that Pacific and Atlantic goliath groupers were the same species, and the argument was settled before the widespread use of genetic techniques," Matthew Craig of the Hawaii Institute of Marine Biology said in a statement.
Craig led the study, which appeared recently in the journal Endangered Species Research.
The goliath groupers split off into two species about three and a half million years ago, when the Atlantic and the Pacific became separated by modern-day Panama.
But the new species may be short-lived, experts warn: The Pacific grouper will likely join the Atlantic grouper as critically endangered on the International Union for the Conservation of Nature's Red List of Threatened Species.